Stimulator handpiece for an evoked potential monitoring system

ABSTRACT

An evoked potential monitoring system including a control unit having stimulator circuitry and a probe assembly coupled to the control unit. The probe assembly includes a stimulus probe and a stimulator handpiece selectively coupled to the stimulus probe. The handpiece includes a handle, control circuitry, and a switch. The control circuitry is electrically coupled to the stimulator circuitry. The switch is electrically coupled to the control circuitry and extends to an exterior portion of the handle. In this regard, movement of the switch remotely controls the stimulator circuitry to continuously increment or decrement a stimulation energy level delivered to the stimulus probe over a series of discrete, incremental steps.

BACKGROUND

The present invention relates to an evoked potential monitoring system.More particularly, it relates to a stimulator handpiece useful as partof an evoked potential monitoring system and to remotely dictate achangeable stimulation energy level delivered by a stimulus probeotherwise carried by the handpiece.

Electrophysiological monitoring assists a surgeon in locating nerveswithin an obscured surgical field, as well as preserving and assessingnerve function in real-time during surgery. To this end, evokedpotential monitoring, such as electromyogram (EMG) monitoring, iscommonly employed. In general terms, sensing or recording electrodes arecoupled to appropriate tissue (e.g., cranial muscles innervated orcontrolled by the nerve of interest, peripheral nerve, spinal cord,brainstem, etc.). Electrical stimulation is then applied near the areawhere the subject nerve may be located. If the stimulation probecontacts or is reasonably near the nerve, the applied stimulation signalis transmitted through the nerve to excite the innervated tissue.Excitement of the related tissue generates an electrical impulse that issensed by the recording electrodes (or other sensing device). Therecording electrode(s) signal the sensed electrical impulse informationto the surgeon for interpretation in the context of evoked potential. Byway of reference, evoked potential is a relatively generic phrase thatgenerally encompasses any system in which a stimulus is applied and apatient's response to the stimulation is recorded. EMG is but one evokedpotential monitoring technique, and can provide additional informationof interest to a surgeon. For example, EMG provides the reporting onindividual nerve roots, whereas evoked potential monitoring, such asmotor evoked potential monitoring, provides feedback on spinal cordfunction.

Evoked potential monitoring is useful for a multitude of differentsurgical procedures or evaluations that involve or relate to nervetissue, muscle tissue, or recording of neurogenic potential. Forexample, various head and neck surgical procedures require locating andidentifying cranial and peripheral motor nerves. Spinal surgicalprocedures often utilize motor evoked potential stimulation (e.g.,degenerative treatments, fusion cages, etc.). While substantial effortshave been made to identify useful implementation of evoked potentialmonitoring, and the analysis of information generated during thesemonitoring procedures, certain aspects of evoked potential monitoringhave remained essentially constant over time. In particular, whilestimulator probes have been modified in terms of size and shape to bestsatisfy anatomical constraints presented by various procedures,operational capabilities of the stimulator handpiece itself continue tobe fairly basic. Namely, the stimulator handpiece maintains thestimulator probe and is electrically connected to a separate controlsource. The surgeon manipulates the handpiece to position the probe, butcan only control stimulation levels at the separate control source.

By way of example, surgery to the spine often necessitates astabilization of the spinal column through the use of reinforcing rodsand plates. The rods and plates are affixed by screws (i.e., “pediclescrews”) fastened to pedicles, or bony surfaces, of selected vertebrae.To facilitate the attachment of the rods and plates, holes for thepedicle screws are bored into the selected vertebrae. The location ofthe pedicle holes is carefully determined to avoid impinging adjacentnerve roots. With this in mind, a surgeon creating pedicle holes has adesire to monitor the location of each pedicle hole and to ensure theintegrity of the adjacent nerve root. Electrical stimulation is commonlyused to evaluate the placement of a pedicle hole.

Current techniques for evaluating pedicle holes via electricalstimulation employ a handpiece maintaining a stimulation probe that iselectrically coupled to a separate control source. The probe is insertedinto a previously formed pedicle hole and stimulation at a first levelapplied thereto via operation of the separate control source. Assumingthat no physical movement of the patient occurs (i.e., no nerveresponse), the stimulation level is incrementally increased, again byoperating the separate power source until a desired, maximum stimuluslevel is applied with no visible patient response. Alternatively,Neubardt, U.S. Pat. No. 5,474,558, described a pedicle hole stimulatorhandpiece maintaining four switches that correlate to on/off, and threediscrete stimulation levels. Use of the Neubartd device relies onphysical movement of the patient to indicate pedicle hole mis-placement,and thus does not represent a true evoked potential monitoring system.Further, the discrete levels of stimulation control afforded by thehandpiece inherently limits the stimulation level, and delivery thereof,desired by the surgeon.

The stimulator handpieces associated with other evoked potentialmonitoring system are similarly limited. Therefore, a need exists for animproved stimulator handpiece useful as part of an evoked potentialmonitoring system.

SUMMARY

One aspect of the present invention is related to an evoked potentialmonitoring system. The system includes a control unit and a probeassembly. The control unit can assume a variety of forms, and includesstimulator circuitry. The probe assembly includes a stimulus probe, anda stimulator handpiece selectively coupled to the stimulus probe. Thehandpiece includes a handle, control circuitry, and a switch. Inparticular, the handle defines an enclosed region. The control circuitryis disposed within the enclosed region and is electrically coupled tothe stimulator circuitry. The switch is electrically coupled to thecontrol circuitry and extends to an exterior portion of the handle. Inthis regard, movement of the switch remotely controls the stimulatorcircuitry to continuously vary a stimulation energy level delivered thestimulus probe, in one embodiment over a series of discrete, sequentialsteps.

Another aspect of the present invention is related to a stimulatorhandpiece for use with an evoked potential monitoring system. Thestimulator handpiece includes a handle, a probe connector, controlcircuitry, and a switch. The handle defines an enclosed region. Theprobe connector is disposed within the enclosed region and is configuredto selectively receive a stimulus probe. The control circuitry isdisposed within the enclosed region and is configured to electricallycommunicate with a control unit. The switch is electrically coupled tothe control circuitry and extends to an exterior portion of the handle,the switch having at least three degrees of freedom. In this regard,movement of the switch remotely varies an electrical signal deliverableto the control unit.

Yet another aspect of the present invention is related to a method ofremotely controlling a stimulus level of an evoked potential monitoringsystem stimulus probe. The method includes the step of providing a probeassembly including a stimulus probe removably coupled to a stimulatorhandpiece. In this regard, the stimulator handpiece includes a handledefining an enclosed region, control circuitry disposed within theenclosed region and electrically coupled to stimulator circuitrydisposed in a remote control unit, and a switch electrically coupled tothe control circuitry and extending to an exterior portion of thehandle. The method additionally includes the step of contacting thestimulus probe with an anatomical body part. The method further includesthe step of moving the switch to vary a stimulation energy leveldelivered by the stimulus probe over a series of discrete, incrementalsteps. Further, a physiological response of the patient to thestimulation energy is electronically recorded.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are better understood with reference to thefollowing drawings. The elements of the drawings are not necessarily toscale relative to each other. Like reference numerals designatecorresponding similar parts.

FIG. 1 is a perspective view of an evoked potential monitoring systemillustrating a probe assembly according to one embodiment of the presentinvention;

FIG. 2 is an exploded view of a probe assembly component of the systemof FIG. 1;

FIG. 3A is an exploded view of a portion of the probe assembly of FIG.2, including a switch coupled to a printed circuit board according toone embodiment of the present invention;

FIG. 3B is a simplified electrical diagram of a portion of the probeassembly of FIG. 2 in accordance with the present invention,illustrating connection of the switch to the printed circuit board;

FIG. 4A is a top view of the probe assembly of FIG. 2 illustratingdegrees of freedom of a switch in accordance with the present invention;

FIGS. 4B-4E are side views of the probe assembly of FIG. 2 illustratingselected movement of a switch through at least one degree of freedomaccording to embodiments of the present invention;

FIG. 5 is a block diagram illustrating operation of a control unit inresponse to signals from the probe assembly of FIG. 2;

FIG. 6 illustrates one application of the evoked potential monitoringsystem in accordance with the present invention, including evaluating apedicle hole;

FIG. 7 is a perspective view of an alternate embodiment probe assemblyemploying a rotating wheel switch in accordance with the presentinvention; and

FIG. 8 is a perspective view of another alternate embodiment probeassembly employing a rocker arm switch in accordance with the presentinvention.

DETAILED DESCRIPTION

An evoked potential monitoring system 10 according to one embodiment ofthe present invention is illustrated in FIG. 1. In general terms, thesystem 10 is configured to assist in and perform evoked potentialmonitoring for virtually any nerve/muscle combination of the humananatomy, as well as recording nerve potential. The system 10 includes acontrol unit 20 and a probe assembly 50. As described in greater detailbelow, the control unit 20 can assume a wide variety of forms and in oneembodiment includes a console 30, having a monitor 32, and a patientinterface module 40. Regardless, the control unit 20 facilitatesoperation of the probe assembly 50, as well as processes all informationgenerated by other system 10 components (not shown) during use. Moreparticularly, the probe assembly 50 and the control unit 20 are adaptedto allow control and variation of a stimulus energy delivered to, andthus an stimulus level delivered by, the probe assembly 50 via anactuator provided on the probe assembly 50 (remote of the control unit20). To this end, the probe assembly 50 and the control unit 20 areadapted to allow continuous variation (e.g., increment or decrement) ofthe stimulation energy over a series of discrete, sequential steps viamanipulation of the probe assembly 50 actuator. Further, when performingan evoked potential monitoring procedure, the control unit 20 processesinformation (e.g., patient response) resulting from deliveredstimulation. For example, the system 10 can include one or more sensingdevices (not shown), such as sensing or recording electrodes, that areemployed to sense or measure a patient's response (if any) tostimulation applied by the probe assembly 50. From these processedresults, an evoked potential evaluation can be performed.

In one embodiment, the system 10 performs monitoring based upon recordedEMG activity in response to an electrical current energy delivered bythe probe assembly 50. Alternatively, the system 10 can be adapted toemploy other evoked potential monitoring techniques (e.g., directlysensing nerve response to stimulation energy applied by the probeassembly 50, etc.). Regardless, with the one embodiment of FIG. 1, theconsole 30 and the patient interface module 40 are provided as separatecomponents, communicatively coupled by a cable 52. Alternatively, awireless link can be employed. Further, the console 30 and the patientinterface module 40 can be provided as a single device. In basic terms,however, the patient interface module 40 serves to promote easyconnection of stimulus/sensory components (such as the probe assembly50), as well as to manage incoming and outgoing electrical signals. Theconsole 30, in turn, interprets incoming signals (e.g., impulses sensedby sensing or recording electrodes), displays information desired by auser, provides a user interface (such as by including, for example, atouch screen), and delivers a stimulation energy to the probe assembly50 pursuant to control signals from the probe assembly 50 (viaconnection to the patient interface module 40), as well as other tasksas desired. The stimulation energy can be continuously increased ordecreased over a series of discrete, sequential steps.

With the above general operational parameters in mind, the console 30 isconfigured to facilitate evoked potential monitoring with at least one,preferably at least four, channels of EMG monitoring. In one embodiment,the console 30 is an alternating current (AC) powered console;alternatively, the console 30 can be battery powered. To this end, theconsole 30 is capable of delivering a stimulation current or voltage tothe probe assembly 50 via the patient interface module 40, and inparticular at varying levels based upon control signals initiated by auser of the probe assembly 50. For example, the console 30 is preferablyadapted to generate a multiplicity of discrete stimulation energy levelsover a range of 0-30 mA in increments of 0.01, 0.05, 1.0, or 5.0 mA. Thesensitivity of the incremental adjustments (i.e., increase or decreasein stimulation energy level) can be selected by the user or can be asingle, pre-determined value (e.g., the console 30 can be adapted tofacilitate variation in the delivered stimulation energy level inincrements of 1.0 mA only). Even further, the console 30 can be adaptedto continuously increase or decrease the stimulation energy level (inresponse to signals from the probe assembly 50) in a non-linear fashion.For example, the console 30 can be adapted to increase or decrease thedelivered stimulation in increments of 0.01 mA for a first time periodfollowed by 1.0 mA incremental changes for subsequent, second timeperiod immediately following the first time period. In one embodiment,the console 30 is further connected to, and controls operation of,auxiliary items such as a printer (not shown) other stimulus probes,etc., in response to control signals from the probe assembly 50 (as wellas by direct operation of the console 30 in one embodiment). Theprocessing of probe assembly control signals by the console 30 isdescribed below.

As previously described, the patient interface module 40 communicateswith the console 30 through the cable 52 information to and from theprobe assembly 50, as well as information from other sensing components(not shown), such as sensing or recording electrodes. In effect, thepatient interface module 40 serves to connect the patient (not shown) tothe console 30. To this end, and in one embodiment, the patientinterface module 40 includes one or more (preferably eight) sensoryinputs 56, such as pairs of electrode inputs (illustrated schematicallyin FIG. 1). In addition, the patient interface module 40 provides asimulator input port 58 (referenced generally in FIG. 1) and astimulator output port 60 (referenced generally in FIG. 1). As describedbelow, the stimulator input port 58 receives control signals from theprobe assembly 50 relating to desired stimulation levels and/or otheractivities, whereas the stimulator output port 60 facilitates deliveryof stimulation energy to the probe assembly 50. The patient interfacemodule 40 can further provide additional component port(s), such as aground (or return electrode) jack, auxiliary ports for additionalstimulator probe assemblies, etc. Conversely, one or more of the ports56-60 can be eliminated (such as where the probe assembly 50 is directlyconnected to the console 30).

The control unit 20, and in particular the console 30 and the patientinterface module 40, are akin in several respects to availablemonitoring systems, such as the NIM-Response™ Nerve Integrity Monitor,available from Medtronic Xomed of Jacksonville, Fla. For example, thetouch screen capabilities provided by the NIM-Response™ Nerve IntegrityMonitor can be incorporated into the control unit 20 of the presentinvention. In addition, however, the system 10 of the present invention,and in particular the probe assembly 50 in combination with appropriatestimulation circuitry associated with the console 30 and/or the patientinterface module 40, affords the surgeon control of the stimulationenergy delivered by the probe assembly 50 on a continuous basis over aseries of discrete, incremental or sequential steps via manipulation ofan actuator provided on the probe assembly 50 itself as part of anevoked potential monitoring operation, features not otherwise providedby available monitoring systems or stimulator handpieces. Thus, thecontrol unit 20 can vary significantly from the one embodiment describedwhile remaining within the scope of the present invention.

The probe assembly 50 is, in one embodiment, a monopolar stimulationdevice and includes a stimulator handpiece 70, a stimulus probe 72selectively coupled to the handpiece 70, cabling 76 extending from thesurgical handpiece 70 and attachable to the patient interface module 40,and control circuitry (not shown in FIG. 1). The stimulator handpiece 70includes a handle 77 maintaining a switch 78.

More specifically, the handle 77 defines a probe end 80 and a cable end82. The cabling 76 extends from the cable end 82 to the patientinterface module 40. Alternatively, the cabling 76 can be coupled to theconsole 30. In a preferred embodiment, the cabling 76 is a dual sectioncable including an energy supply cable 84 and a control cable 86. Afirst strain relief harness 88 is provided to reinforce the energysupply cable 84, and a second strain relief harness 89 is provided toreinforce the control cable 86. As a point of reference, the energysupply cable 84 is configured to couple with the stimulator output port60 and the control cable 86 is configured to couple with the stimulatorinput port 58 of the patient interface module 40.

FIG. 2 is an exploded view of the probe assembly 50 according to oneembodiment of the present invention. In particular, in the view of FIG.2, the stimulation handpiece 70 has been disassembled to describe theorientation and relationship of the various components. In this regard,the handle 77 includes a first section 100 and a second section 102 eachconfigured for mating attachment to the other. When assembled, the firstand second sections 100, 102 collectively form the probe end 80, thecable end 82, and an enclosed region 106.

In one embodiment, the handle sections 100, 102 are formed of a durableengineering plastic suited for repeated cleaning and/or sterilization.Exemplary engineering plastics for forming the handle 77 includehigh-density polyethylene, acrylonitrile butadiene styrene (ABS), nylonin general, and polyester in general. In an alternate embodiment, thehandle 77 is formed of a durable and rust resistant metal, for examplestainless steel. Even further, the handle 77 can be integrally formed asa homogenous body.

A probe connector 108 is formed by the handle sections 100, 102 withinthe enclosed region 106 adjacent to the probe end 80 and is configuredto selectively receive the stimulus probe 72. As a point of reference,corresponding portions of the probe connector 108 are, in oneembodiment, formed by each of the handle section 100, 102, although onlythe portion associated with the section 100 is visible in the view ofFIG. 2. The probe connector 108 is preferably a quick release probeconnector such that the stimulus probe 72 can easily be disposed offollowing use and/or replaced with a differently configured stimulusprobe 72. Alternatively, a more permanent assembly between the probeconnector 108 and the stimulus probe 72 can be provided. In oneembodiment, the probe connector 108 includes an engagement surface 109suited for engaging an engagement shaft 110 of the stimulus probe 72.Further, the energy supply cable 84 terminates in a connector (notshown), such as a Molex connector, adapted to electrically couple theenergy supply cable 84 to the stimulus probe 72 upon final assembly.Regardless, the stimulus probe 72 can be any one of a variety of tissue,bone, and/or nerve stimulator probes. Therefore, while the stimulusprobe 72 is depicted as a ball point nerve probe, it is to be understoodthat other shapes and sizes of probes useful for supplying stimulationenergy to muscle, tissue, and/or nerves are equally appropriate for usewith the surgical handpiece 70. For example, the stimulus probe 72 canalternatively be a Prass flush tip probe, Kartush stimulus dissector(KSC Instruments), a Yingling flex tip probe, a modified stimulationprobe, etc. Even further, the probe assembly 50, including the stimulusprobe 72, can be configured as a bipolar stimulation device.

As shown in FIG. 1, control circuitry 112 including a printed circuitboard 114 is disposed within the enclosed region 106 and is electricallycoupled to the control cable 86 (that, in one embodiment, includes abundle of six wires). As described above, the cabling 76 is preferably adual section cable including the energy supply cable 84 and the controlcable 86. With this in mind, when the stimulator handpiece 70 isassembled, the energy supply cable 84 electrically communicates with thestimulus probe 72, and the control cable 86 bifurcates from the energysupply cable 84 to electrically couple with the printed circuit board114. In this manner, the control circuitry 112 within the enclosedregion 106 is physically separated from the stimulator circuitry (notshown) within the control unit 20 (FIG. 1).

The printed circuit board 114 is electrically connected to the controlcable 86 and controls electrical signals sent from the switch 78 to thestimulator circuitry (not shown) housed in the control unit 20 (FIG. 1).In particular, the printed circuit board 114 is electrically coupled tothe switch 78 such that the control circuitry 112 prompts delivery ofstimulation energy to the stimulus probe 72 in response to movements ofthe switch 78, as described below. Notably, while the control circuitry112 is operatively coupled to the control unit 20, the control circuit112 is electrically isolated from the patient and the surgeon duringuse.

FIG. 3A is an exploded view of the switch 78 connected to the printedcircuit board 114. In one embodiment, the switch 78 is amulti-directional, momentary action switch and includes an actuator 115,a post 116 and a pad 117. The actuator 115 is electrically connected tothe printed circuit board 114 via terminals 118. In one embodiment, theterminals 118 are gullwing terminals suitable for being soldered to theprinted circuit board 114. The post 116 is pivotally mounted to theactuator 115 via a sealed joint 119. In one embodiment, the sealed joint119 is a polymeric sealed joint permitting the post 116 to gyrate inrelation to the actuator 115. The pad 117 slidably fits over the post116 and is ergonomically shaped to permit deft manipulation of theswitch 78. Switches suitable for implementing embodiments of the presentinvention include TPA Series Navigation Tact Switches available from,for example, ITT Industries, Inc., White Plains, N.Y.

With additional reference to FIG. 2, when the stimulator handpiece 70 isassembled, the switch 78 is assembled to the handle 77 such that thepost 116 extends from the enclosed region 106 to an exterior portion ofthe handle 77 where the post 116 is capped by the pad 117. The handle 77and the pad 117 combine to seal the surgical handpiece 70 againstentrance of liquids possibly encountered during a surgical procedure.Manipulation of the pad 117 moves the post 116 relative to the actuator115. The actuator 115 translates movement of the post 116 into anelectrical signal that is communicated through the control cable 86 tothe control unit 20 (FIG. 1). The stimulator circuitry (not shown)within the control unit 20 interprets the electrical signal and respondswith an electrical command that is transferred through the energy supplycable 84 to the stimulus probe 72 and/or to other components (e.g., aprinter, additional stimulator probe, other surgical device, etc.). Inthis manner, movement of the switch 78 at the surgical handpiece 70triggers a remote response from the stimulator circuitry in the controlunit 20.

In one embodiment, the switch 78 can assume (i.e., move or pivotbetween) at least a forward position, a rearward position, and a neutralposition, and can be depressed downward when in any one of the forward,rearward, or neutral positions. Even further, the switch 78 is operablebetween left and right positions (relative to the neutral position).Once again, “movement” of the switch 78 is characterized as the post 116moving relative to the actuator 115 via manipulation of the pad 117. Thesimplified wiring diagram of FIG. 3B illustrates one possible electricalconnection of the actuator 115 to the printed circuit board 114,including an indication of possible terminal 118 designations orcommands.

In a preferred embodiment, the switch 78 gyrates through a range ofpositions, as described below. For example, FIG. 4A is a top view of theprobe assembly 50 illustrating the switch 78 in a neutral position. FIG.4A further illustrates that the switch 78 can be moved longitudinally tooccupy a forward distal position 140 and, alternately, a rearwardproximal position 141 (movement to the positions is indicated by arrows140 and 141, respectively). In this regard, the longitudinal movement ofthe switch 78 to the distal forward 140 and the proximal rearward 141positions entails two degrees of freedom referred to as a pitchmovement. In one embodiment, the switch 78 can pitch from the neutralposition a distance of approximately 0.5 mm to the distal forward 140position and a can pitch a similar distance of approximately 0.5 mm tothe proximal rearward 141 position, although the probe assembly 50 canbe configured to provide other pitch dimensions.

In addition, the switch 78 can be moved laterally as indicated by arrow142. The lateral movement of the switch 78 indicated by the arrow 142entails two degrees of freedom (i.e., left and right in the orientationof FIG. 4A) referred to as a roll movement. In one embodiment, theswitch 78 can roll laterally from the neutral position a distance ofapproximately 0.5 mm in each of the lateral (i.e., left and right)directions as indicated by the arrow 142, although the probe assembly 50can be configured to provide other roll dimensions.

Moreover, the switch 78 moves flexibly via the sealed joint 119 (FIG. 3)and can be depressed downward (i.e., directed into the paper) and canrebound upward, and entails two degrees of freedom (i.e., downward andupward) referred to as an axial movement. In one embodiment, the switch78 can move axially when in any of the forward, rearward, or lateralpositions. In view of the above, in one embodiment, the switch 78 ismovable through a range of motions defined by six degrees of freedom.

FIGS. 4B-4E are each a side view of the probe assembly 50 shown in FIG.1 during use. The side view of FIG. 4B illustrates a hand 150 of asurgeon holding the surgical handpiece 70 such that a finger, forexample an index finger 152, is positioned to manipulate the switch 78and in particular the pad 117. As illustrated in FIG. 4B, the switch 78is in the neutral position and the index finger 152 is posed forselective manipulation of the switch 78 at the discretion of thesurgeon. In this regard, during use when the switch 78 in the neutralposition, the system 10 (FIG. 1) is adapted to maintain a currentstimulation energy (or stimulus level) setting delivered to, and thusby, the stimulus probe 72 (i.e., a static stimulus level, for example astimulus level previously selected by the surgeon upon initiation of thesystem 10). The static stimulus level can be any stimulation energylevel available with the system 10, including no stimulation energy, andmovement of the switch 78 varies the stimulus level delivered to thestimulus probe 72 from the static stimulus level.

FIG. 4C is a side view the probe assembly 50 showing the switch 78pitched distally to a forward position. In this regard, the index finger152 is shown displacing the switch 78 toward the stimulus probe 72. Inone embodiment, displacement of the switch 78 to the forward positioncauses the actuator 115 (FIG. 3A) to signal the control circuitry 112(FIG. 2) to send a signal to the stimulator circuitry in the controlunit 20 (FIG. 1), triggering or prompting an increment (i.e., anincrease) in the electrical current, and thus the stimulus level,delivered to the stimulus probe 72. In one embodiment, the system 10(FIG. 1) is adapted such that when the switch 78 is retained (i.e.,held) in the forward position, the stimulus level delivered to thestimulus probe 72 is continuously increased over a series of discrete,incremental steps. As described below, in one embodiment, the system 10(FIG. 1) is adapted such that where the switch 78 is held in the forwardposition for an extended period of time, the rate at which the deliveredstimulus level increases occurs more rapidly (e.g., the incrementalsteps in stimulus level become larger).

FIG. 4D is a side view of the probe assembly 50 showing the switch 78pitched proximally to a rearward position. In one embodiment,displacement of the switch 78 to the rearward position causes theactuator 115 (FIG. 3) to signal the control circuitry 112 (FIG. 2) tosend a signal to the stimulator circuitry in the control unit 20 (FIG.1), triggering or prompting a continuous decrement (i.e., decrease) inthe electrical current, and thus the stimulation energy, delivered tothe stimulus probe 72. When the switch 78 is retained (i.e., held) inthe rearward position, the system 10 (FIG. 1) is adapted such that thestimulation energy delivered to, and thus by, the stimulus probe 72 iscontinuously decremented over a series of discrete, incremental steps.

FIG. 4E is a side view of the probe assembly 50 illustrating the switch78 in a depressed position. In particular, the index finger 152 of thesurgeon is depressing the switch 78 axially to the depressed position.In one embodiment, the system 10 (FIG. 1) is adapted such that pressingthe switch 78 downward signals or prompts the control unit 20 to operatean auxiliary item. For example, pressing the switch 78 downward canprompt the control unit 20 to generate a printout of informationdisplayed on the monitor 32 (FIG. 1), such as by controlling operationof a separate printer (not shown). In this manner, information ofinterest to the surgeon (e.g., current stimulation settings, evokedpotential readings, EMG activity readings, etc.) can be captured forarchival purposes during any instant of the surgical procedure.Alternatively, a wide variety of other operations can be prompted bypressing of the switch, such as saving information to a disk, initiate amonitoring sequence of another piece of equipment otherwise connected tothe control unit 20 (e.g., SSEP monitoring), control stimulus level of aseparate probe, etc.). In addition, in one embodiment, pressing theswitch 78 downward and holding for an extended period of time (e.g., atleast one second) is interpreted by the control unit 20 as a request toterminate the delivery of stimulation energy to the stimulus probe 72,resulting in a stimulus level of zero mA. As a point of reference, theswitch 78 can be depressed downward when the switch 78 is in any one ofthe forward, neutral, or rearward positions such that the surgeon canselectively print the information displayed on the monitor 32 orterminate electrical stimulation at any point in the procedure.

With the above descriptions of the switch 78 in mind, the probe assembly50 is operable by the surgeon to apply the desired stimulus level to ananatomical feature, continuously increment or decrement the stimuluslevel over a series of discrete, incremental steps, terminate thestimulus or maintain the desired stimulation current, prompt operationof an auxiliary device (e.g., print the associated display screen datafrom the monitor 32), and/or zero the stimulus level of the stimulusprobe 72 during intraoperative evoked potential monitoring events.Alternately, other actions can be facilitated and/or one or more of thefeatures described above can be eliminated. For example, the system 10(FIG. 1) can be adapted such that roll movements of the switch 78 promptother activities/operational features via the control unit and/or othersystem components (e.g., changing or toggling between display screens onthe monitor 32, altering operational parameters (e.g., probe orelectrode sensitivity), etc.). Even further, the probe assembly 50 caninclude one or more additional switches (not shown), that may or may notbe identical to the switch 78, on the handpiece 70 that facilitate oneor more of the auxiliary actions described above (or any other featureassociated with the control unit 20 (FIG. 1)).

In one embodiment, the switch 78 is a joystick movable through at leastthree degrees of freedom, preferably through six degrees of freedom, asdescribed above. In particular, the switch 78 can be translated and/orrotated and/or depressed across a full range of pitch, roll, and axialmovements such that the switch 78 is not limited to linear movements. Inthis manner, movement of the switch 78 enables the surgeon otherwisehandling the probe assembly 50 during an evoked potential monitoringprocedure to remotely and continuously control the stimulus leveldelivered to the stimulus probe 72 over a series of discrete,incremental steps.

In one embodiment, the system 10 is programmed to have a defaultstimulation frequency of 5 Hz, a pulse duration of 100 microseconds, anda stimulus current level that is adjustable via the switch 78 from 0-30mA in increments of 0.05, 0.01, 1.0, or 5.0 mA. In one embodiment, theprobe assembly 50 is a monopolar stimulation probe configured such thatthe electrical current is delivered through the stimulus probe 72 andreturns to a ground electrode (not shown) attached to the patient. In analternate embodiment, the probe assembly 50 is a bipolar probe suitedfor general use as a nerve locator. In any regard, the probe assembly 50has a frequency range of 1-10 Hz, preferably the frequency is deliveredat 5 Hz, and a pulse duration in the range of 50-250 microsecondsadjustable in 50 microsecond increments, and a stimulus current leveladjustable in the range of 0-30 mA via manipulation of the switch 78through one of at least three degrees of freedom.

As previously described, the control unit 20 (FIG. 1), for example theconsole 30 and/or the patient interface module 40, includes stimulatorcircuitry and related software/hardware for receiving, interpreting, andacting in response to signals from the probe assembly 50, and inparticular signals generated by manipulation of the switch 78. With thisin mind, FIG. 5 is a simplified block diagram illustrating operation ofthe stimulation circuitry/programming in accordance with one embodimentof the present invention. At step 300, the system 10 (FIG. 1) isactivated, followed by initialization of the stimulation circuitrycontrol parameters at step 302. In particular, the stimulationprogramming initializes a “Repeat_Delay_Time” value that otherwisedesignates the length of time the switch 78 (FIG. 2) must remain in aparticular position (e.g., pitched forward or rearward, rolled left orright, etc.) before an action is taken by the control unit 20. TheRepeat_Delay_Time value can be a default number (e.g., 0.5 second) orcan be designated by the user. Further, the stimulation programminginitially designates that a state of the switch is “inactive” (i.e.,“Select_State”); as described below, the “state” can be “press”(interpreted as a request to generate a screen print out), “zeroed”(interpreted as a request to cease the deliver of stimulation energy),or “inactive” (interpreted as being status quo, whereby stimulationenergy is delivered to the probe assembly 50 and no screen print outsare being generated).

At step 304, a signal from the probe assembly 50 (FIG. 1) is read. Inparticular, any signal generated by the switch 78 (FIG. 2) istransferred via the control cable 86 (FIG. 2) to the stimulationcircuitry/programming, such as via the patient interface module 40 (FIG.1). Once again, the switch 78 is remote of the control unit 20 (FIG. 1),and is manipulated in a desired fashion by the surgeon. Regardless, theread switch signal is interpreted at steps 306-312.

For example, at step 306, a determination is made as to whether the readswitch signal is indicative of the switch 78 (FIG. 2) being in thepitched forward position of FIG. 4C (designated as “UP position”) inFIG. 5. If “yes”, at step 314 the length of time the switch 78 has beenin the pitched forward position is compared to the “Repeat_Delay_Time”value. If the time period the switch 78 has been in the pitched forwardposition is less than the Repeat_Delay_Time value (“no” at step 314),the stimulator programming returns to step 304 and continues to read theswitch signal. Conversely, if the switch 78 has been in the pitchedforward position for a time period greater than the Repeat_Delay_Timevalue (“yes” at step 314), the control unit 20 operates to incrementallyincrease the stimulation energy delivered to the probe assembly 50, andin particular the stimulus probe 72 (FIG. 2), at step 316 over theseries of discrete, sequential energy level steps available with thecontrol unit 20. Further, the display provided to the surgeon via thecontrol unit 20 is updated to reflect the increased stimulation energylevel. Subsequently, at step 318, the “Repeat_Delay_Time” value is“marked” or held until the switch signal (at step 304) is identified asbeing something other than the pitched forward position; under thesecircumstances, then, the stimulation energy level will continue toincrease over the discrete, incremental series of energy level stepsuntil a switch signal other than “pitched forward” is sensed. In oneembodiment, “marking” of the Repeat_Delay_Time value facilitates anon-linear increase in the delivered stimulation energy level over time.For example, for the stimulator circuitry/programming can be adaptedsuch that for the first two seconds the switch 78 is in the pitchedforward position, the energy level increases in increments of 0.01 mA;for the next five seconds the switch 78 is in the pitched forwardposition, the energy level increases in increments of 0.05 mA; inincrements of 1.0 mA for the next five seconds; and increments of 5.0 mAthereafter. Once the switch 78 is release from the pitched forwardposition, the rate of increase returns to the smallest incrementalchange value. Alternatively, the energy level can increase inincremental steps linearly over time with the switch 78 in the forwardposition.

Step 308 relates to the switch signal reflecting the switch 78 (FIG. 2)being maneuvered to the pitched rearward position of FIG. 4D (designatedas “DOWN position” in FIG. 5). In particular, a determination is made asto whether the read switch signal is indicative of the switch 78 beingin the pitched forward position. If “yes”, at step 320 the length oftime the switch 78 has been in the pitched rearward position is comparedto the “Repeat_Delay_Time” value. If the time period the switch 78 hasbeen in the pitched rearward position is less than the Repeat_Delay_Timevalue (“no” at step 320), the stimulator programming returns to step 304and continues to read the switch signal. Conversely, if the switch 78has been in the pitched rearward position for a time period greater thanthe Repeat_Delay_Time value (“yes” at step 320), the control unit 20operates to incrementally decrease the stimulation energy delivered tothe probe assembly 50, and in particular the stimulus probe 72 (FIG. 2),at step 322. Further, the display provided to the surgeon via thecontrol unit 20 is updated to reflect the decreased stimulation energylevel. Subsequently, at step 318, the “Repeat_Delay_Time” value is“marked” or held until the switch signal (at step 304) is identified asbeing something other than the pitched rearward position; under thesecircumstances, then, the stimulation energy level will continue todecrease until a switch signal other than pitched rearward is sensed.The rate of continuous, incremental decrease in the stimulation energylevel with the switch 78 in the pitched rearward position can benon-linear or linear over time as described above with respect tooperation in the pitched forward position.

Step 310 relates to the switch signal (read at step 304) reflecting theswitch 78 (FIG. 2) being depressed (“SELECT (press)”). If it is detectedthat the switch 78 has been pressed (“yes” at step 310), reference ismade to the current setting of “Select_State” at step 324. If it isdetermined that the current Select_State setting is “Inactive” (“yes” atstep 324), the “Select_State” value is changed to “Press” at step 326.Also, the “Select_Time” value is marked, meaning that a length of timethe switch 78 is maintained in the pressed position begins to berecorded. Subsequently, the switch signal is again read at step 304. Ifthe switch signal indicates that the switch 78 is no longer beingpressed (“no” at step 310), reference is made to the Select_Statedesignation at step 328. If the Select_State is “Press” (“yes” at step328, recalling that the Select_State could previously be designated as“Press” at step 326), the control unit 20 (FIG. 1) is operated to causean attached printer (not shown) to print out current information, suchas information displayed on the monitor 32 (FIG. 1) at step 330.Alternatively, instead of prompting a print function, step 330 canprompt operation of a multitude of other functions associated with thecontrol unit 20, such as printing the screen display of an image guidedsurgery piece of equipment, activation of or control over a separatestimulus probe, initiating a monitoring sequence, etc. Further,“Select_State” is re-set to “Inactive”. In this manner, then, thecontrol unit 20 can be prompted to print desired information (or performthe designated auxiliary function) by simply depressing and releasingthe switch 78 regardless of a pitch or roll position.

Conversely, following step 326 above, if, following setting of theSelect_State to “Press”, the switch signal continues to indicate thatthe switch 78 (FIG. 2) is pressed (“yes” at step 310), at step 324 adetermination is made that the “Select_State” is not “Inactive” (“no” atstep 324). Under these circumstances, a confirmation is made at step 332that the “Select_State” designation is “Press”. If the Select_Statedesignation is something other than “Press” (“no” at step 332), theswitch signal is again read at step 304. If the Select_State designationis “Press” (“yes” at step 332), the current Select_Time value (i.e., thelength of time the switch 78 has been continuously held in the pressedposition) is compared to a predetermined “HOLD_TIME” threshold value(otherwise indicative of the length of time the switch 78 must remaindepressed before an energy cessation action is taken) at step 334. Ifthe Select_Time value does not exceed the “HOLD_TIME” value (“no” atstep 334), no action is taken, and the switch signal is again read atstep 304. If the Select_Time value exceeds the HOLD_TIME threshold value(“yes” at step 334), the control unit 20 (FIG. 1) operates to stopdelivery of stimulation energy to the probe assembly 50 (FIG. 2) at step336, meaning that stimulation by the stimulus probe 72 (FIG. 2) ceases.Further, the “Select_State” is assigned a “Zeroed” designation, and theswitch signal is again read at step 304. Subsequently, once the switchsignal indicates that the switch 78 is no longer in the pressed position(i.e., “no” at step 310), the “Select_State” is re-designated as“Inactive” at steps 338 and 340.

Finally, if the switch signal read at step 304 indicates that the switch78 (FIG. 2) has been rolled left or right (“yes” at step 312), otheractions can be taken as desired. This had been generically designated as“expanded functionality” at step 342.

It will be recognized that the flow diagram of FIG. 5 represents but onemethodology for interpreting and acting upon signals from the probeassembly 50 (FIG. 2), and in particular the switch 78 (FIG. 2), inaccordance with the present invention. A wide variety of other actionscan be taken, and switch signals varying from those specificallydescribed can be employed. Further, some of the functionality describedin FIG. 5 (such responses to pressing of the switch and/or left or rightrolled positions) can be eliminated. In a most basic form, the controlunit 20, and in particular the stimulator circuitry and relatedprogramming, is adapted to receive signals from a remote switch providedon or by the probe assembly 50, and facilitate continuous increase ordecrease in delivered stimulation energy in response to the switchsignals over a series of discrete, incremental steps.

One possible use of the probe assembly 50 employed as part of an evokedpotential monitoring system is described with reference to FIG. 6. FIG.6 depicts an enlarged posterior view of skeletal members of a lumbarspinal region 180 of a human patient. The lumbar spinal region 180includes a first lumbar vertebra 182, a second lumbar vertebra 184, athird lumbar vertebra 186, a fourth lumbar vertebra 188, a fifth lumbarvertebra 190, and a sacrum 192 comprised of fused vertebrae. A pedicle194 of the fourth lumbar vertebra 188 is provided with a pedicle hole196 as part of a spinal stabilization procedure. The pedicle hole 196 isformed by the surgeon and may be tapped (i.e., threaded), or enlarged,as the surgical procedure indicates.

To evaluate placement of the pedicle hole 196, the evoked potentialmonitoring system 10 (FIG. 1) of the present invention can be employed.In one embodiment, sensing or recording electrodes (not shown) areplaced on the patient at appropriate locations for sensing impulses(e.g., at or along muscles, the spinal column, peripheral nerves, etc.).Further, a ground electrode (not shown) is attached to the patient. Thesystem 10 is then initiated. The surgeon manipulates the stimulatorhandpiece 70 and inserts the stimulus probe 72 into the pedicle hole196. The surgeon can initiate electrical stimulation to the stimulusprobe 72 by moving the switch 78. The stimulus level delivered to thestimulus probe 72 can be continuously incremented or decremented over aseries of discrete, incremental steps by an appropriate movement of theswitch 78, as best described with reference to FIG. 4A above. Inaddition, the surgeon can print the data (“print screen”) from themonitor 32 (FIG. 1) or prompt a different feature by momentarilydepressing the switch 78. In this regard, the monitor 32 visuallyindicates to the surgeon the stimulus levels, and other data, related tothe stimulus probe 72.

During an exemplary evoked potential monitoring procedure, the surgeonselectively increments or decrements the stimulus level delivered to thestimulus probe 72 by pitching and/or rolling the switch 78 in theappropriate direction. For example, the surgeon can hold the switch 78in the pitched forward position for a first period of time until thestimulation energy incrementally approaches a desired value. The surgeoncan then briefly move to and release the switch 78 from the pitchedforward position and/or pitched rearward position until the desiredstimulation energy level is obtained. Following monitoring of the evokedpotential at this stimulus level, the surgeon can, where desired,further increase the stimulation energy level by holding the switch 78in the pitched forward position for another length of time, repeatingthe monitoring process. Finally, the surgeon can terminate the stimulusenergy delivered to the stimulus probe 72 by depressing and holding theswitch 78 for more than one second. In this manner, the surgeon can,remote of the control unit 20 (FIG. 1) continuously vary and control theelectrical stimulation level delivered to, and thus by, the stimulusprobe 72 over a series of discrete incremental steps via movement of theswitch 78. Throughout the procedure, the evoked potential is monitoredby the surgeon. If minimal or no reaction to the stimulation energy issensed by the system 10, the surgeon can make a determination that thepedicle hole 196 is acceptable. Conversely, if an evoked potential issensed by the system 10, the surgeon may determine that an alternativelocation for the pedicle hole 196 should be selected.

The pedicle hole evaluation procedure described above is but onepossible application of the evoked potential monitoring system 10 (FIG.1), and in particular the probe assembly 50, in accordance with thepresent invention. A multitude of other evoked potential monitoringprocedures will equally benefit from the present invention. Examples ofsuch procedures include, but are not limited to, monitoring the opticnerve, monitoring the extraocular nerves, monitoring the trigeminalnerve, monitoring the facial nerves (for example, as part of earsurgery), monitoring the cochlear nerve, monitoring the vagus nerve,monitoring the spinal accessory nerve, monitoring the hypoglossal nerve,spinal cord monitoring, monitoring the recurrent laryngeal nerve,thyroid and parathyroid gland surgery, etc., to name but a few.

FIG. 7 is a perspective view of an alternate probe assembly 200 inaccordance with the present invention. The probe assembly 200 includes astimulator handpiece 202 having a wheel switch 204. The wheel switch 204is analogous to the joy stick-type switch 78 (FIG. 2) previouslydescribed is movable through a range of pitch and axial movements. Inparticular, the wheel switch 204 includes an actuator (not shown, butanalogous to the actuator 115 (FIG. 3A) previously described) coupled tothe control circuitry 112 (FIG. 2) within the stimulator handpiece 202such that the pitch and axial movements of the switch 204 causes theactuator to signal the stimulator circuitry in the control unit 20(FIG. 1) to remotely and continuously vary the stimulus level deliveredto the stimulus probe 72 over a series of discrete, incremental steps,substantially as described above for the pitch and axial movements ofthe probe assembly 50 (FIG. 1).

FIG. 8 is a perspective view of another alternative embodiment probeassembly 210 in accordance with the present invention. The probeassembly 210 includes a stimulator handpiece 212 having a rocker switch214. The rocker switch 214 is movable through a range of pitch and axialmovements. In particular, the rocker switch 214 includes an actuator(not shown, but analogous to the actuator 115 of FIG. 3A) couple to thecontrol circuitry 112 (FIG. 2) within the stimulator handpiece 212 suchthat the pitch and axial movements of the rocker switch 214 causes theactuator to signal the stimulator circuitry in the control unit 20(FIG. 1) to remotely and continuously vary the stimulus level deliveredto the stimulus probe 72 over a series of discrete, incremental steps,substantially as described above for the pitch and axial movements ofthe probe assembly 50 (FIG. 1).

Although specific embodiments of a stimulator handpiece for evokedpotential monitoring have been illustrated and described, it will beappreciated by those of ordinary skill in the art that a variety ofalternate and/or equivalent implementations could be substituted for thespecific embodiments shown and described without departing from thescope of the present invention. Therefore, this application is intendedto cover any adaptations or variations of stimulator handpieces andsystems for evoked potential monitoring having a switch for the remoteand continuous control of a stimulus level delivered to a stimulusprobe. It is intended that this invention be limited only by the claimsand the equivalents thereof.

1. An evoked potential monitoring system comprising: a control unitincluding stimulator circuitry; and a probe assembly electricallycoupled to the control unit, the probe assembly including: a stimulusprobe, and a stimulator handpiece selectively maintaining the stimulusprobe, the handpiece including: a handle defining an enclosed region,control circuitry disposed within the enclosed region and electricallyconnected to the stimulator circuitry, a switch electrically coupled tothe control circuitry and extending to an exterior portion of thehandle; wherein the system is adapted such that movement of the switchremotely prompts the stimulator circuitry to continuously vary astimulation energy level delivered to the stimulus probe.
 2. The evokedpotential monitoring system of claim 1, wherein the stimulus probe is anerve probe.
 3. The evoked potential monitoring system of claim 1,wherein the probe assembly is a monopolar probe assembly.
 4. The evokedpotential monitoring system of claim 1, wherein the probe assembly is abipolar probe assembly.
 5. The evoked potential monitoring system ofclaim 1, wherein the control unit is adapted to record a patient'sresponse to stimulation energy delivered by the stimulus probe.
 6. Theevoked potential monitoring system of claim 1, wherein the system isadapted such that movement of the switch continuously varies thestimulation energy level delivered to the stimulus probe over a seriesof discrete, sequential steps.
 7. The evoked potential monitoring systemof claim 6, wherein the system is adapted such that the switch can beoperated to select any of the discrete, incremental stimulation energylevel steps available through the control unit.
 8. The evoked potentialmonitoring system of claim 6, wherein the system is adapted to incrementor decrement the stimulation energy level delivered to the stimulusprobe in a non-linear fashion in response to movement of the switch. 9.The evoked potential monitoring system of claim 6, wherein the system isadapted to automatically increase or decrease the stimulation energylevel delivered to the stimulus probe in a sequential fashion inresponse to movement of the switch.
 10. The evoked potential monitoringsystem of claim 1, wherein the system is adapted such that movement ofthe switch increments the stimulation energy level delivered by thestimulus probe.
 11. The evoked potential monitoring system of claim 1,wherein the system is adapted such that movement of the switchdecrements the stimulation energy level delivered by the stimulus probe.12. The evoked potential monitoring system of claim 1, wherein thestimulus probe is operable in a stimulating state and a non-stimulatingstate, and further wherein the system is adapted such that depressingand holding the switch ceases delivery of stimulation energy to thestimulus probe.
 13. The evoked potential monitoring system of claim 1,further comprising an auxiliary device connected to the control unit,and further wherein the system is adapted such that depressing theswitch causes the control unit to prompt operation of the auxiliarydevice.
 14. The evoked potential monitoring system of claim 1, whereinthe stimulator handpiece further comprises cabling extending from thehandle and configured to couple to the control unit.
 15. The evokedpotential monitoring system of claim 14, wherein the cabling is a dualcable defining an energy supply cable and a control cable, the controlcircuitry electrically coupled to the control cable, and further whereinboth the energy supply cable and the control cable are electricallycoupled to the control unit.
 16. The evoked potential monitoring systemof claim 1, wherein the switch includes: an actuator; a post extendingfrom the actuator; and a pad coupled to the post.
 17. The evokedpotential monitoring system of claim 1, wherein the switch is configuredto pitch longitudinally and roll laterally.
 18. The evoked potentialmonitoring system of claim 1, wherein the switch is a pivoting rockerarm extending from the enclosed region to an exterior portion of thehandle.
 19. The evoked potential monitoring system of claim 1, whereinthe switch is a finger wheel mounted within the enclosed region andextending to an exterior portion of the handle.
 20. The evoked potentialmonitoring system of claim 1, wherein the switch has four degrees offreedom.
 21. The evoked potential monitoring system of claim 1, whereinthe switch has more than four degrees of freedom.
 22. A stimulatorhandpiece for use with an evoked potential monitoring system, thehandpiece comprising: a handle defining an enclosed region; a probeconnector disposed within the enclosed region and configured toselectively receive a stimulus probe; control circuitry disposed withinthe enclosed region and configured to electrically communicate with acontrol unit; and a switch electrically coupled to the control circuitryand extending to an exterior portion of the handle, the switch having atleast three degrees of freedom; wherein movement of the switch remotelyvaries an electrical signal deliverable to the control unit.
 23. Thestimulator handpiece of claim 18, wherein the switch includes: anactuator; a post extending from the actuator; and a pad coupled to thepost.
 24. The stimulator handpiece of claim 19, wherein the post ismoveable relative to the actuator.
 25. The stimulator handpiece of claim20, wherein the actuator is adapted to generate differing signalsdepending upon a position of the post relative to the actuator.
 26. Thestimulator handpiece of claim 18, wherein the switch is configured topitch longitudinally and roll laterally.
 27. The stimulator handpiece ofclaim 18, wherein the handpiece is characterized by a single switch. 28.A method of remotely controlling a stimulus level of an evoked potentialsystem stimulus probe, the method comprising: providing a probe assemblyincluding a stimulus probe removably coupled to a stimulator handpiece,the stimulator handpiece including: a handle defining an enclosedregion, control circuitry disposed within the enclosed region andelectrically coupled to stimulator circuitry disposed in a remotecontrol unit, a switch electrically coupled to the control circuitry andextending to an exterior portion of the handle; contacting the stimulusprobe with an anatomical body part; moving the switch to vary astimulation energy level delivered by the stimulus probe; andelectronically recording a physiological response of the patent to thedelivered stimulation energy.
 29. The method of claim 28, wherein movingthe switch includes triggering the control circuitry to communicate withstimulator circuitry.
 30. The method of claim 28, wherein moving theswitch prompts a continuous change in the stimulation energy deliveredby the stimulus probe over a series of discrete, incremental steps. 31.The method of claim 28, further comprising holding the switch in a firstposition to continuously increase the stimulation energy level deliveredby the stimulus probe over a series of discrete, incremental steps. 32.The method of claim 28, further comprising holding the switch in a firstposition to continuously decreased the stimulation energy leveldelivered by the stimulus probe over a series of discrete, incrementalsteps.
 33. The method of claim 28, further comprising toggling theswitch to achieve a desired stimulation energy level delivered by thestimulus probe.
 34. The method of claim 28, wherein the stimulus probecontacts a muscle.
 35. The method of claim 28, wherein the stimulusprobe contacts a nerve.